Control chip for touch panel with high sensitivity and operating method thereof

ABSTRACT

There is provided a capacitive touch device including a touch panel and a control chip. The touch panel includes a detection electrode configured to form a self-capacitor. The control chip includes an emulation circuit and a subtraction circuit. The emulation circuit is configured to output a reference signal. The subtraction circuit is coupled to the emulation circuit and the detection electrode, subtracts the reference signal outputted by the emulation circuit from a detected signal outputted by the detection electrode to output a differential detected signal, and identifies a touch event according to an amplified differential detected signal so as to improve the touch sensitivity.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 15/080,718, filed on Mar. 25, 2016, which claims the prioritybenefit of Taiwan Patent Application Serial Number 104109783, filed onMar. 26, 2015, the full disclosure of which is incorporated herein byreference.

BACKGROUND 1. Field of the Disclosure

This disclosure generally relates to a touch device, more particularly,to a capacitive touch device with high sensitivity and an operatingmethod thereof.

2. Description of the Related Art

Because a user can operate a touch panel by intuition, the touch panelhas been widely applied to various electronic devices. In general, thetouch panel is classified into capacitive, resistive and optical touchpanels.

The capacitive touch sensor is further classified into self-capacitivetouch sensors and mutual capacitive touch sensors. These two kinds oftouch sensors have different characteristics of the capacitivevariation, so they are adaptable to different functions. For example,the mutual capacitive touch sensors are adaptable to the multi-touchdetection, and the self-capacitive touch sensors have a highersensitivity to hovering operations and a lower sensitivity to waterdrops. However, how to improve the touch sensitivity of these two kindsof capacitive touch sensors is an important issue.

SUMMARY

Accordingly, the present disclosure provides a capacitive touch devicewith high sensitivity and an operating method thereof.

The present disclosure provides a capacitive touch device and anoperating method thereof in which an emulation circuit is arranged in acontrol chip to generate a reference signal as a cancellation of adetection signal, and thus a size of a detection capacitor in thecontrol chip is reduced.

The present disclosure provides a capacitive touch device and anoperating method thereof in which an emulation circuit is arranged in acontrol chip to generate a reference signal as a cancellation of adetection signal, and thus a touch sensitivity is improved.

The present disclosure provides a control chip for a touch panel. Thetouch panel includes a detection electrode configured to form aself-capacitor. The control chip includes an input resistor, anamplifying circuit and an emulation circuit. The input resistor isconfigured to be coupled to an output end of the detection electrode.The amplifying circuit is connected with the input resistor. Theemulation circuit is configured to directly receive a drive signal andnot connected to the output end of the detection electrode. The inputresistor and the amplifying circuit are configured to form a firstfilter circuit with the self-capacitor. The emulation circuit isconfigured to form a second filter circuit. The frequency response ofthe second filter circuit is determined according to a frequencyresponse of the first filter circuit.

The present disclosure further provides a control chip for a touchpanel. The touch panel includes a plurality of detection electrodesrespectively configured to form a self-capacitor. The control chipincludes an emulation circuit, a plurality of programmable filters and asubtraction circuit. The emulation circuit is not connected to signaloutputs of the detection electrodes and configured to directly receive adrive signal and output a reference signal. The plurality ofprogrammable filters is respectively coupled to the signal outputs ofthe detection electrodes. The subtraction circuit is directly connectedto the emulation circuit, and configured to be sequentially coupled tothe programmable filters in a self-capacitive mode, and perform adifferential operation on the reference signal outputted by theemulation circuit and a detection signal outputted by the coupledprogrammable filter to output a differential detected signal.

The present disclosure further provides an operating method of a controlchip for a touch panel. The touch panel includes a plurality of driveelectrodes and a plurality of receiving electrodes extending alongdifferent directions. The control chip includes an emulation circuit, aplurality of detection capacitors, a subtraction circuit and ananti-aliasing filter. The operating method includes the steps of:respectively coupling, in a self-capacitive mode, a first drive signalto first ends of the drive electrodes via the detection capacitors andrespectively coupling the subtraction circuit to second ends of thedrive electrodes; directly inputting, in the self-capacitive mode,another drive signal to the emulation circuit, which is not connected tothe second ends of the drive electrodes, to output a reference signal;and respectively coupling, in a mutual capacitive mode, the first drivesignal to the first ends of the drive electrodes without passing thedetection capacitors, and respectively coupling the anti-aliasing filterto second ends of the receiving electrodes without passing thesubtraction circuit.

A capacitive touch device of the present disclosure is adaptable to atouch device which uses only a self-capacitive detection mode, and to atouch device which uses a dual-mode detection including theself-capacitive detection mode and a mutual capacitive detection mode.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages, and novel features of the present disclosurewill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

FIG. 1 is a schematic block diagram of a capacitive touch deviceaccording to one embodiment of the present disclosure.

FIG. 2 is a schematic block diagram of a capacitive touch deviceaccording to one embodiment of the present disclosure.

FIG. 3 is another schematic block diagram of a capacitive touch deviceaccording to one embodiment of the present disclosure.

FIG. 4A is the waveform of a detection signal and a reference signal inthe capacitive touch device of the embodiments of FIGS. 2 and 3.

FIG. 4B is a waveform of a differential detected signal of the detectionsignal and the reference signal in FIG. 4A.

FIG. 5 is a flow chart of an operating method of a capacitive touchdevice according to one embodiment of the present disclosure.

FIG. 6 is a frequency response of a filter circuit of a capacitive touchdevice according to one embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENT

It should be noted that, wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Please refer to FIG. 1, it is a schematic block diagram of a capacitivetouch device according to one embodiment of the present disclosure. Thecapacitive touch device 1 includes a control chip 100 and a touch panel13, wherein the capacitive touch device 1 is preferably able to detectby a self-capacitive mode. In some embodiments, the capacitive touchdevice 1 is able to detect approaching objects and distinguish touchpositions by successively using a self-capacitive mode and a mutualcapacitive mode. For example, in some embodiments, because a scanninginterval of the self-capacitive mode is short, the capacitive touchdevice 1 is able to identify whether any object is approaching using theself-capacitive mode. After an approaching object is identified, a touchposition is identified using the mutual capacitive mode. In otherembodiments, the capacitive touch device 1 is able to identify a roughposition of an approaching object and determine a window of interest(WOI) on the touch panel 13 with the self-capacitive mode, and thenidentify a fine position within the window of interest with the mutualcapacitive mode to reduce data amount to be processed in the mutualcapacitive mode. It should be mention that implementations of theself-capacitive mode and the mutual capacitive mode mentioned above areonly intended to illustrate, but not to limit the present disclosure.

The touch panel 13 includes a plurality of detection electrodes 131 torespectively form a self-capacitor C_(s), wherein the detectionelectrodes 131 include a plurality of drive electrodes and a pluralityof receiving electrodes extending along different directions, e.g.,perpendicular to each other. Mutual capacitors C_(m) (referring to FIGS.2 and 3) are formed between the drive electrodes and the receivingelectrodes. The principle of forming self-capacitors and mutualcapacitors in a capacitive touch panel is known and is not an object ofthe present disclosure, and thus details thereof is not describedherein.

The control chip 100 includes a plurality of drive circuits 11, aplurality of detection capacitors C_(in) and an emulation circuit 150,wherein the emulation circuit 150 is used to emulate the characteristicsof the detection line in a self-capacitive mode (described hereinafter).In the self-capacitive mode, the drive circuits 11 and the detectioncapacitors C_(in) are electrically coupled to signal inputs of thedetection electrodes 131 via pins. The drive circuits 11 output a drivesignal Sd, e.g., a sine wave, a cosine wave or a square wave to thedetection electrodes 131. In a mutual capacitive mode, only the drivecircuit 11 corresponding to the drive electrode outputs the drive signalSd, whereas the drive circuit 11 corresponding to the receivingelectrode is bypassed.

Please refer to FIG. 2, it is a schematic block diagram of a capacitivetouch device according to one embodiment of the present disclosure. Asmentioned above, the capacitive touch device 1 includes a touch panel 13and a control chip 100. The control chip 100 includes a plurality ofdrive circuits 11, a plurality of detection capacitors C_(in), an analogfront end 15 and a digital back end 16, wherein as the digital back end16 is not an object of the present disclosure, details thereof are notdescribed herein. In the present disclosure, the drive circuits 11 areable to be electrically coupled to signal inputs of the detectionelectrodes 131 via the detection capacitors C_(in) (e.g. in theself-capacitive mode) or bypassing the detection capacitors C_(in) (e.g.in the mutual capacitive mode), wherein said coupled to and bypassingthe detection capacitors C_(in) is able to be implemented by arranging aplurality of switches SW₁ between the drive circuits 11 and the touchpanel 13.

The analog front end 15 includes an emulation circuit 150, a pluralityof programmable filters 151, a subtraction circuit 52, a gain circuit153 and an anti-aliasing filter (AAF) 154. The programmable filters 151,the detection capacitors C_(in) and the self-capacitors C_(s) of thedetection electrodes 131 form a first filter circuit, wherein the firstfilter circuit is, e.g., a band-pass filter (BPF) or a high-pass filter(HPF). The first filter circuit is able to further form a band-passfilter having a predetermined bandwidth with a low-pass filter formed bythe anti-aliasing filter 154. In one embodiment, the signal output ofeach detection electrode 131 is coupled to (e.g. via a switch) oneprogrammable filter 151. It should be mentioned that although only thehorizontally arranged detection electrodes 131 shown in FIGS. 2 and 3are coupled to the programmable filters 151, in other embodiments theprogrammable filters 151 are also coupled to the longitudinally arrangeddetection electrodes 131, and the present disclosure is not limited tothose shown in FIGS. 2 and 3.

The emulation circuit 150 forms a second filter circuit and outputs areference signal S_(ref), wherein the second filter circuit is, e.g., aband-pass filter or a high-pass filter. The second filter circuit isable to further form a band-pass filter having a predetermined bandwidthwith a low-pass filter formed by the anti-aliasing filter 154. Thesubtraction circuit 152 is coupled to the emulation circuit 150 and issequentially and electrically coupled to the programmable filters 151via switches SW₂ in a self-capacitive mode to be further electricallycoupled to the detection electrodes 131. The subtraction circuit 152performs a differential operation on the reference signal S_(ref)outputted by the emulation circuit 150 and a detection signal S_(ol)outputted by the coupled programmable filter 151 to output adifferential detected signal S_(diff). To be more precisely, in thepresent disclosure, the detection capacitors C_(in) are respectively andelectrically coupled to signal inputs of the detection electrodes 131via a plurality of switches (e.g. SW₁), and the subtraction circuit 152is respectively and electrically coupled to the programmable filters 151and the detection electrodes 131 via a plurality of switches (e.g. SW₂).

In the present disclosure, the detection capacitor C_(in) is disposed inthe control chip 100 to form the voltage division with theself-capacitor C_(s). Accordingly, the capacitive touch device 1identifies a touch event according to a variation of peak-to-peak valuesof the differential detected signal S_(diff), wherein the differentialdetected signal S_(diff) is a continuous signal. Before a touch event isidentified, the differential detected signal S_(diff) is furtherfiltered or digitized. For example, FIG. 2 shows the toucheddifferential detected signal S_(touch) and the non-touched differentialdetected signal S_(non). However, as the self-capacitor C_(s) isgenerally very large, an effective voltage division is implemented byusing a large detection capacitor C_(in). Therefore, the considerabledisposition space in the chip for the large capacitor is necessary suchthat a total size of the control chip 100 is unable to be reduced.

Accordingly, in the present disclosure, the circuit characteristics ofthe detection line (e.g. from the drive circuit 11 via the detectioncapacitor C_(in), the detection electrode 131 and the programmablefilter 151) is emulated by disposing the emulation circuit 150 to outputthe reference signal S_(ref) as a cancellation of the detection signalS_(ol), as shown in FIG. 4. The capacitance of the detection capacitorC_(in) is able to be decreased by subtracting the cancellation from thedetection signal S_(ol). For example, the capacitance of the detectioncapacitor C_(in) is preferably smaller than 10 percent of capacitance ofthe self-capacitor C_(s). Therefore, the size of the control chip 100 iseffectively decreased.

To make a difference between the touched differential detected signalS_(touch) and the non-touched differential detected signal S_(non) bemore obvious, in some embodiments a gain circuit 153 is employed toamplify the differential detected signal S_(diff), wherein a gain of thegain circuit 153 is determined according to an analytical range of ananalog-to-digital convertor (ADC) of the digital back end 16, but notlimited thereto. As shown in FIG. 2, the difference between the toucheddifferential detected signal S_(touch) and the non-touched differentialdetected signal S_(non), which are signals (i.e. differential detectedsignal) outputted by the gain circuit 153, is increased such that atouch event is easier to be identified. The anti-aliasing filter 154filters the amplified differential detected signal and, as mentionedabove, the anti-aliasing filter 154 is, for example, a low-pass filter.

Please refer to FIG. 3, it is another schematic block diagram of acapacitive touch device according to one embodiment of the presentdisclosure, wherein FIG. 3 further shows an implementation of theemulation circuit 150 and the programmable filter 151.

In some embodiments, the programmable filter 151 includes an inputresistor R_(in) and an amplifying circuit 15A, wherein the detectioncapacitor C_(in), the self-capacitor C_(s), the input resistor R_(in)and the amplifying circuit 15A form a first filter circuit, and theemulation circuit 150 forms a second filter circuit. As mentioned above,the subtraction circuit 152 performs a differential operation on adetection signal S_(ol) outputted by the first filter circuit and areference signal S_(ref) outputted by the second filter circuit tooutput a differential detected signal S_(diff), as shown in FIGS. 4A and4B, wherein FIG. 4B shows a waveform of a differential detected signalS_(diff) of the detection signal S_(ol) and the reference signal S_(ref)shown in FIG. 4A.

In one embodiment, the amplifying circuit 15A includes an operationalamplifier OP, a feedback resistor Rf and a compensation capacitor Cf.The feedback resistor Rf and the compensation capacitor Cf are connectedbetween a negative input and an output of the operational amplifier OP.The input resistor R_(in) is coupled between a second end (i.e. thesignal output) of the detection electrode 131 and the negative input ofthe operational amplifier OP. A first end (i.e. the signal input) of thedetection electrode 131 is coupled to the detection capacitor C_(in). Inthis embodiment, a frequency response of the first filter circuit isindicated by equation (1) and the Bode diagram of FIG. 6, wherein thefirst filter circuit has two poles and a zero, which is located at 0.(v _(out) /v _(in))=−(Rf/R _(in))x(s·C _(in) ·R_(in))/(1+s·Rf·Cf)x(1+s·R _(in) ·C _(s) +S·R _(in) ·C _(in))  (1)

As mentioned above, because an output of the emulation circuit 150 isused as a cancellation of the first filter circuit, the frequencyresponse of the emulation circuit 150 is preferably similar to that ofthe first filter circuit, i.e. the frequency response of the emulationcircuit 150 is determined according to a frequency response of the firstfilter circuit. In some embodiments, the two frequency responses aresimilar is referred to, for example, two poles of the emulation circuit150 being close to two poles of the first filter circuit, but notlimited thereto. For example, the two poles of the emulation circuit 150are determined according to the two poles of the first filter circuit,and because the zero is not affected, only the pole frequencies areconsidered. For example, differences between pole frequencies of twopoles of the emulation circuit 150 and frequencies of poles, whichcorrespond to the two poles of the emulation circuit 150, of the secondfilter circuit is designed to be below 35 percent of the polefrequencies of the emulation circuit 150, and preferably to be below 20percent. Although the two poles of the emulation circuit 150 are closeto the two poles of the first filter circuit as much as possible, sinceit is difficult to precisely know the self-capacitor C_(s) of eachdetection electrode 131 in advance, the emulation circuit 150 isdesigned by estimation.

In one embodiment, the emulation circuit 150 includes an emulationdetection capacitor C_(ref_in), an emulation self-capacitor C_(ref_s),an emulation input resistor R_(ref_in) and an emulation amplifyingcircuit 15B, and connections between the emulation detection capacitorC_(ref_in), the emulation self-capacitor C_(ref_s), the emulation inputresistor R_(ref_in) and the emulation amplifying circuit 15B arearranged based on connections between the detection capacitor C_(in),the self-capacitor C_(s), the input resistor R_(in) and the amplifyingcircuit 15A to obtain a similar frequency response without particularlimitations, e.g., having identical connections. That is, the emulationself-capacitor C_(ref_s) is used to emulate self-capacitor C_(s) of thedetection electrode 131, the emulation detection capacitor C_(ref_in) isused to emulate the detection capacitor C_(in), the emulation inputresistor R_(ref_in) corresponds to the input resistor R_(in), and theemulation amplifying circuit 15B corresponds to the amplifying circuit15A. It should be mentioned that the circuit parameter of the emulationcircuit 150 (i.e. RC value) is not necessary to be completely the sameas the circuit parameter of the first filter circuit, as long as thefrequency response of the emulation circuit 150 is similar to thefrequency response of the first filter circuit, and the detectioncapacitor C_(s) is decreased without particular limitations.

The emulation amplifying circuit 15B also includes an operationalamplifier OP′, an emulation feedback resistor R_(ref_f) and an emulationcompensation capacitor C_(ref_f), wherein connections of elements in theemulation amplifying circuit 15B are arranged based on those of theamplifying circuit 15A without particular limitations, e.g., havingidentical connections. Therefore, a second filter circuit formed by theemulation circuit 150 also has a similar frequency response as theequation (1) and the Bode diagram of FIG. 6. The difference is that allelement parameters of the emulation circuit 150 are predesigned.Accordingly, positions of two poles are adjustable by changing theelement parameters, i.e. resistance and capacitance, of the emulationcircuit 150.

Please refer to FIG. 5, it is a flow chart of an operating method of acapacitive touch device according to one embodiment of the presentdisclosure, including a self-capacitive mode (step S₅₁) and a mutualcapacitive mode (step S₅₂). In this embodiment, the self-capacitive modeand the mutual capacitive mode is separately operated, e.g., firstlyidentifying an approaching object and/or a window of interest (WOI)using the self-capacitive mode and identifying a touch positions and/ora gesture using the mutual capacitive mode.

In the self-capacitive mode, the drive circuits 11 are respectively andelectrically coupled to first ends of the drive electrodes via thedetection capacitors C_(in), and the subtraction circuit 152 isrespectively and electrically coupled to second ends of the driveelectrodes. Meanwhile, because the subtraction circuit 152 receives areference signal S_(ref) outputted by the emulation circuit 150 and thesubtraction circuit 152 is electrically coupled to the second end of thedrive electrodes via a programmable filter 151, the subtraction circuit152 performs a differential operation on a detection signal S_(ol)outputted by the programmable filter 151 and the reference signalS_(ref) outputted by the emulation circuit 150 to output a differentialdetected signal S_(diff), as shown in FIGS. 4A and 4B. Then, a gaincircuit 153 amplifies the differential detected signal S_(diff) to makea difference between a touched differential detected signal S_(touch)and a non-touched differential detected signal S_(non) be moresignificant, as shown in FIG. 2. Furthermore, in one embodiment, a touchevent is identified by detecting detection signals outputted by aplurality of drive electrodes or a plurality of receiving electrodes tooperate in a shorter scanning period.

In another embodiment, detection signals outputted by a plurality ofdrive electrodes and a plurality of receiving electrodes are detected toidentify a window of interest (WOI) on the touch panel in aself-capacitive mode. Therefore, in the self-capacitive mode, the drivecircuits 11 are respectively and electrically coupled to the first ends(i.e. signal inputs) of the receiving electrodes via the detectioncapacitors C_(in), and the subtraction circuit 152 is sequentially andelectrically coupled to second ends (i.e. signal outputs) of thereceiving electrodes. The window of interest is determined afteridentifying the drive electrode and the receiving electrode that sensean approaching object. As mentioned above, in the present disclosure thedrive electrodes and the receiving electrodes are both belong to thedetection electrodes 131 to generate mutual capacitors C_(m)therebetween.

In the mutual capacitive mode, the drive circuits 11 are respectivelyand electrically coupled to the first ends of the drive electrodeswithout passing the detection capacitors C_(in). For example in FIGS. 2and 3, the drive circuits 11 bypass the detection capacitor C_(in) usinga switch SW₁ and directly input the drive signal S_(d) to the detectionelectrode 131. Besides, the anti-aliasing filter 154 is respectively andelectrically coupled to the second ends of the drive electrodes withoutpassing the subtraction circuit 152. For example in FIGS. 2 and 3, theanti-aliasing filter 154 bypasses the subtraction circuit 152 (and thegain circuit 153) using another switch SW₂ to allow the detection signalS_(ol) outputted by the programmable filter 151 to be directly outputtedto the anti-aliasing filter 154. The filter parameter of theanti-aliasing filter 154 is determined according to actual applicationswithout particular limitation.

In the present disclosure, in the self-capacitive mode because signalssent to the detection lines do not pass resistors and capacitors of thepanel, a phase difference between the reference line (i.e. emulationcircuit) and the detection line is not obvious. Therefore, the referencesignal S_(ref) is used as a cancellation to be subtracted from adetection signal.

It should be mentioned that, although the amplitude (or peak-to-peakvalue) of a non-touched differential detected signal S_(non) is shown tobe larger than the amplitude (or peak-to-peak value) of a toucheddifferential detected signal S_(touch) in FIG. 2, it is only intended toillustrate but not to limit the present disclosure. According to theparameter setting of the emulation circuit 150 (i.e. RC value), it ispossible that the amplitude of the touched differential detected signalS_(touch) is larger than the amplitude of the non-touched differentialdetected signal S_(non).

It should be mentioned that although the amplitude (or peak-to-peakvalue) of a detection signal S_(ol) is shown to be larger than theamplitude (or peak-to-peak value) of a reference signal S_(ref) in FIG.4A, it is only intended to illustrate but not to limit the presentdisclosure. According to the parameter setting of the emulation circuit150 (i.e. RC value), it is possible that the amplitude of the referencesignal S_(ref) is larger than the amplitude of the detection signalS_(ol).

As mentioned above, how to improve the touch sensitivity of a capacitivetouch device is an important issue. Therefore, the present disclosureprovides a capacitive touch device (FIGS. 1 to 3) and an operatingmethod thereof (FIG. 5) that generate a cancellation by disposing anemulation circuit in a control chip to decrease a size of a capacitor inthe control chip used in the self-capacitive mode and improve the touchsensitivity.

Although the disclosure has been explained in relation to its preferredembodiment, it is not used to limit the disclosure. It is to beunderstood that many other possible modifications and variations can bemade by those skilled in the art without departing from the spirit andscope of the disclosure as hereinafter claimed.

What is claimed is:
 1. A control chip for a touch panel, the touch panelcomprising a detection electrode configured to form a self-capacitor,the control chip comprising: an input resistor coupled to an output endof the detection electrode; an amplifying circuit connected with theinput resistor; a subtraction circuit; a switch connected between theamplifying circuit and the subtraction circuit, the switch is locateddownstream of the amplifying circuit; and an emulation circuit fordirectly receiving a drive signal and not connected to the output end ofthe detection electrode; wherein the input resistor and the amplifyingcircuit form a first filter circuit with the self-capacitor foroutputting a detection signal from the amplifying circuit, the emulationcircuit forms a second filter circuit for outputting reference signal,and a frequency response of the second filter circuit is determinedaccording to the first filter circuit; wherein the subtraction circuitperforms a differential operation between the reference signal and thedetection signal outputted from the amplifying circuit in aself-capacitive mode to improve touch sensitivity, the differentialoperation in the self-capacitive mode is performed by coupling thesubtraction circuit to the amplifying circuit using the switch; andwherein a detection operation is performed in a mutual-capacitive modeby bypassing the subtraction circuit, wherein the subtraction circuit isbypassed by decoupling the subtraction circuit to the amplifying circuitusing the switch.
 2. The control chip as claimed in claim 1, furthercomprising a gain circuit for amplifying the differential detectedsignal.
 3. The control chip as claimed in claim 2, wherein the controlchip is to identify a touch event according to a variation ofpeak-to-peak values of the amplified differential detected signal. 4.The control chip as claimed in claim 1, further comprising a detectioncapacitor coupled to an input end of the detection electrode, whereincapacitance of the detection capacitor is smaller than 10 percent ofcapacitance of the self-capacitor.
 5. The control chip as claimed inclaim 1, wherein the first filter circuit has two poles each has a polefrequency, and the second filter circuit has two poles each has a polefrequency corresponding to the pole frequencies of the two poles of thefirst circuit; and wherein differences between the pole frequencies ofthe two poles of the first filter circuit and that of the second filtercircuit are lower than 35 percent of the pole frequencies of the firstfilter circuit.
 6. The control chip as claimed in claim 1, wherein theamplifying circuit comprises an operational amplifier, a feedbackresistor, and a compensation capacitor; wherein the feedback resistorand the compensation capacitor are connected between a negative inputand an output of the operational amplifier, and the input resistor iscoupled between the output end of the detection electrode and thenegative input of the operational amplifier.
 7. The control chip asclaimed in claim 1, wherein the emulation circuit comprises: anemulation detection capacitor connected to a node and configured todirectly receive the drive signal; an emulation self-capacitor connectedbetween the node and ground; an emulation input resistor has a first endconnected to the node; and an emulation amplifying circuit connected toa second end of the emulation input resistor.
 8. A control chip for atouch panel, the touch panel comprising a plurality of detectionelectrodes respectively configured to form a self-capacitor, the controlchip comprising: an emulation circuit not connected to signal outputs ofthe detection electrodes, for directly receiving a drive signal, and foroutputting a reference signal; a plurality of programmable filtersrespectively coupled to the signal outputs of the detection electrodes;a plurality of switches respectively located downstream of theprogrammable filters and connected to the programmable filters; and asubtraction circuit, directly connected to the emulation circuit andlocated downstream of the plurality of switches; wherein the subtractioncircuit performs a differential operation in a self-capacitive mode foroutputting a differential detected signal according to the referencesignal outputted by the emulation circuit and a detection signaloutputted by the coupled programmable filter, wherein the differentialoperation in the self-capacitive mode is performed by coupling thesubtraction circuit to the programmable filters sequentially using theplurality of switches; and wherein a detection operation is performed ina mutual-capacitive mode by bypassing the subtraction circuit, whereinthe subtraction circuit is bypassed by decoupling the subtractioncircuit to the plurality of programmable filters using the plurality ofswitches.
 9. The control chip as claimed in claim 8, further comprisinga gain circuit for amplifying the differential detected signal.
 10. Thecontrol chip as claimed in claim 9, wherein the control chip is toidentify a touch event according to a variation of peak-to-peak valuesof the amplified differential detected signal.
 11. The control chip asclaimed in claim 8, wherein each programmable filter comprises an inputresistor and an amplifying circuit.
 12. The control chip as claimed inclaim 11, further comprising a plurality of detection capacitors to berespectively coupled to signal inputs of the detection electrodes,wherein each of the programmable filters and the detection capacitorsare to form a first filter circuit with the self-capacitor of thecoupled detection electrode.
 13. The control chip as claimed in claim12, wherein the emulation circuit is to form a second filter circuit,and a frequency response of the second filter circuit is determinedaccording to a frequency response of the first filter circuit.
 14. Thecontrol chip as claimed in claim 12, wherein capacitance of thedetection capacitors is smaller than 10 percent of capacitance of theself-capacitor.
 15. The control chip as claimed in claim 12, wherein thedetection capacitors are respectively coupled to the signal inputs ofthe detection electrodes via a plurality of first switches.
 16. Anoperating method of a control chip for a touch panel, the touch panelcomprising a plurality of drive electrodes and a plurality of receivingelectrodes extending along different directions, and the control chipcomprising an emulation circuit, a plurality of detection capacitors, asubtraction circuit, switches coupled between the receiving electrodesand the subtraction circuit, and an anti-aliasing filter, the operatingmethod comprising: coupling, in a self-capacitive mode, a first drivesignal to first ends of the drive electrodes via the detectioncapacitors, and coupling the subtraction circuit to second ends of thedrive electrodes; inputting, in the self-capacitive mode, a second drivesignal to the emulation circuit for outputting a reference signal,wherein the emulation circuit is not connected to the second ends of thedrive electrodes; and coupling, in a mutual capacitive mode, the firstdrive signal to the first ends of the drive electrodes without passingthe detection capacitors, and coupling the anti-aliasing filter tosecond ends of the receiving electrodes by bypassing the subtractioncircuit using the switches.
 17. The operating method as claimed in claim16, further comprising: coupling, in the self-capacitive mode, the firstdrive signal to first ends of the receiving electrodes via the detectioncapacitors, and coupling, in the self-capacitive mode, the subtractioncircuit to the second ends of the receiving electrodes.
 18. Theoperating method as claimed in claim 16, wherein the control chipfurther comprises a plurality of programmable filters connected atupstream of the subtraction circuit, the subtraction circuit iselectrically coupled to the second ends of the drive electrodes via theswitches and the programmable filters respectively, and the operatingmethod further comprises: performing a differential operation foroutputting a differential detected signal accordingly to a detectionsignal outputted by the coupled programmable filter and the referencesignal outputted by the emulation circuit; amplifying the differentialdetected signal; and identifying a touch event according to a variationof peak-to-peak values of the amplified differential detected signal.19. The operating method as claimed in claim 18, wherein theprogrammable filters and the detection capacitors form a first filtercircuit with the self-capacitors of the drive electrodes, the emulationcircuit forms a second filter circuit, and a frequency response of thesecond filter circuit is determined according to the first filtercircuit.